The smaller and more rigid CNC 3018-Pro should be able to engrave text faster than the larger and rather springy MPCNC, which could engrave text at about 50 mm/min. This test pattern pushes both cutting depth and engraving speed to absurd values:
Compile the GCMC source to generate G-Code, lash a CD / DVD to the platform (masking tape works fine), touch off the XY coordinates in the center, touch off Z=0 on the surface, then see what happens:
The “engraving depth” translates directly into the force applied to the diamond point, because the spring converts displacement into force. Knowing the Z depth, you can calculate or guesstimate the force.
Early results from the 3018 suggest it can engrave good-looking text about 20 times faster than the MPCNC:
You must trade off speed with accuracy on your very own machine, as your mileage will certainly differ!
The GCMC source code as a GitHub Gist:
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| // Engraving test piece | |
| // Ed Nisley KE4ZNU - 2019-09 | |
| //----- | |
| // Command line parameters | |
| // -D OuterDia=number | |
| if (!isdefined("OuterDia")) { | |
| OuterDia = 120mm - 2mm; // CD = 120, 3.5 inch drive = 95 | |
| } | |
| OuterRad = OuterDia / 2.0; | |
| comment("Outer Diameter: ",OuterDia); | |
| comment(" Radius: ",OuterRad); | |
| //----- | |
| // Library routines | |
| include("tracepath.inc.gcmc"); | |
| include("engrave.inc.gcmc"); | |
| //----- | |
| // Bend text around an arc | |
| function ArcText(TextPath,Center,Radius,BaseAngle,Align) { | |
| PathLength = TextPath[-1].x; | |
| Circumf = 2*pi()*Radius; | |
| TextAngle = to_deg(360 * PathLength / Circumf); | |
| AlignAngle = BaseAngle + (Align == "Left" ? 0 : | |
| Align == "Center" ? -TextAngle / 2 : | |
| Align == "Right" ? -TextAngle : | |
| 0); | |
| ArcPath = {}; | |
| foreach(TextPath; pt) { | |
| if (!isundef(pt.x) && !isundef(pt.y) && isundef(pt.z)) { // XY motion, no Z | |
| r = Radius - pt.y; | |
| a = 360deg * (pt.x / Circumf) + AlignAngle; | |
| ArcPath += {[r*cos(a) + Center.x, r*sin(a) + Center.y,-]}; | |
| } | |
| elif (isundef(pt.x) && isundef(pt.y) && !isundef(pt.z)) { // no XY, Z up/down | |
| ArcPath += {pt}; | |
| } | |
| else { | |
| error("Point is not pure XY or pure Z: " + to_string(pt)); | |
| } | |
| } | |
| return ArcPath; | |
| } | |
| //----- | |
| // Set up for drawing | |
| SafeZ = 10.0mm; // above clamps and screws | |
| TravelZ = 1.0mm; // above workpiece | |
| PlotZ = -0.5mm; // tune for best results | |
| TextSpeed = 1000mm; // intricate detail | |
| DrawSpeed = 2000mm; // smooth curves | |
| TextFont = FONT_HSANS_1_RS; | |
| TextSize = [2.0mm,2.0mm]; | |
| TextLeading = 2*TextSize.y; // line spacing | |
| DiskCenter = [0mm,0mm]; // middle of the platter | |
| InnerDia = 40mm; | |
| InnerRad = InnerDia / 2.0; | |
| comment("Inner Diameter: ",InnerDia); | |
| comment(" Radius: ",InnerRad); | |
| NumRings = ceil((OuterRad - (InnerRad + TextLeading))/TextLeading); // number of rings to draw | |
| comment("Numer of rings: ",NumRings); | |
| if (1) { | |
| comment("Text Size begins"); | |
| feedrate(TextSpeed); | |
| ts = "Text size: " + to_string(TextSize); | |
| tp = scale(typeset(ts,TextFont),TextSize); | |
| tpa = ArcText(tp,DiskCenter,OuterRad,90deg,"Left"); | |
| engrave(tpa,TravelZ,PlotZ); | |
| } | |
| if (1) { | |
| comment("Depth variations begin"); | |
| TextRadius = OuterRad; | |
| pz = 0.0mm; | |
| repeat(NumRings ; i) { | |
| comment(" depth: " + to_string(pz)); | |
| feedrate(TextSpeed); | |
| ts = "Depth: " + to_string(pz) + " at " + to_string(TextSpeed) + "/min"; | |
| tp = scale(typeset(ts,TextFont),TextSize); | |
| tpa = ArcText(tp,DiskCenter,TextRadius,-5deg,"Right"); | |
| engrave(tpa,TravelZ,pz); | |
| feedrate(DrawSpeed); | |
| goto([0,-TextRadius,-]); | |
| move([-,-,pz]); | |
| arc_ccw([-TextRadius,0,-],-TextRadius); | |
| goto([-,-,TravelZ]); | |
| feedrate(TextSpeed); | |
| tp = scale(typeset("Rad: " + to_string(TextRadius),TextFont),TextSize); | |
| tpa = ArcText(tp,DiskCenter,TextRadius,180deg,"Right"); | |
| engrave(tpa,TravelZ,PlotZ); | |
| TextRadius -= TextLeading; | |
| pz -= 0.10mm; | |
| } | |
| } | |
| if (1) { | |
| comment("Feedrate variations begin"); | |
| TextRadius = OuterRad; | |
| ps = 250mm; | |
| repeat(NumRings ; i) { | |
| comment(" speed: " + to_string(ps) + "/min"); | |
| feedrate(ps); | |
| ts = "Speed: " + to_string(ps) + "/min at " + to_string(PlotZ); | |
| tp = scale(typeset(ts,TextFont),TextSize); | |
| tpa = ArcText(tp,DiskCenter,TextRadius,5deg,"Left"); | |
| engrave(tpa,TravelZ,PlotZ); | |
| TextRadius -= TextLeading; | |
| ps += 250mm; | |
| } | |
| } | |
| if (1) { | |
| comment("Off-center text arcs begin"); | |
| feedrate(TextSpeed); | |
| tc = [-40mm/sqrt(2),-40mm/sqrt(2)]; // center point | |
| r = 3mm; | |
| s = [0.5mm,0.5mm]; | |
| ts = "Radius: " + to_string(r) + " Size: " + to_string(s); | |
| tp = scale(typeset(ts,TextFont),s); | |
| tpa = ArcText(tp,tc,r,0deg,"Center"); | |
| engrave(tpa,TravelZ,PlotZ); | |
| r = 5mm; | |
| s = [1.0mm,1.0mm]; | |
| ts = "Radius: " + to_string(r) + " Size: " + to_string(s); | |
| tp = scale(typeset(ts,TextFont),s); | |
| tpa = ArcText(tp,tc,r,0deg,"Center"); | |
| engrave(tpa,TravelZ,PlotZ); | |
| r = 8mm; | |
| s = [1.5mm,1.5mm]; | |
| ts = "Radius: " + to_string(r) + " Size: " + to_string(s); | |
| tp = scale(typeset(ts,TextFont),s); | |
| tpa = ArcText(tp,tc,r,0deg,"Center"); | |
| engrave(tpa,TravelZ,PlotZ); | |
| r = 15mm; | |
| s = [3.0mm,3.0mm]; | |
| ts = "Radius: " + to_string(r) + " Size: " + to_string(s); | |
| tp = scale(typeset(ts,FONT_HSCRIPT_2),s); | |
| tpa = ArcText(tp,tc,r,0deg,"Center"); | |
| engrave(tpa,TravelZ,PlotZ); | |
| } | |
| if (1) { | |
| comment("Attribution begins"); | |
| feedrate(TextSpeed); | |
| tp = scale(typeset("Ed Nisley - KE4ZNU - softsolder.com",TextFont),TextSize); | |
| tpa = ArcText(tp,DiskCenter,15mm,0deg,"Center"); | |
| engrave(tpa,TravelZ,PlotZ); | |
| tp = scale(typeset("Engraving Test Disc",TextFont),TextSize); | |
| tpa = ArcText(tp,DiskCenter,15mm,180deg,"Center"); | |
| engrave(tpa,TravelZ,PlotZ); | |
| } | |
| goto([-,-,SafeZ]); | |
| goto([0mm,0mm,-]); | |
| comment("Done!"); |
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| #!/bin/bash | |
| # Engraving test pattern generator | |
| # Ed Nisley KE4ZNU - 2019-08 | |
| Diameter='OuterDia=116mm' | |
| Flags='-P 3 --pedantic' | |
| # Set these to match your file layout | |
| LibPath='/opt/gcmc/library' | |
| Prolog='/mnt/bulkdata/Project Files/CNC 3018-Pro Router/Patterns/gcmc/prolog.gcmc' | |
| Epilog='/mnt/bulkdata/Project Files/CNC 3018-Pro Router/Patterns/gcmc/epilog.gcmc' | |
| Script='/mnt/bulkdata/Project Files/CNC 3018-Pro Router/Patterns/Engraving Test.gcmc' | |
| ts=$(date +%Y%m%d-%H%M%S) | |
| fn='TestPattern_'${ts}'.ngc' | |
| echo Output: $fn | |
| rm -f $fn | |
| echo "(File: "$fn")" > $fn | |
| /opt/gcmc/src/gcmc -D $Diameter $Flags \ | |
| --include "$LibPath" --prologue "$Prolog" --epilogue "$Epilog" \ | |
| "$Script" >> $fn | |
The Smell of Molten Projects in the Morning 
Looking really good Ed. Nice job. Congrats on getting your new toy working so well. Of course we knew you would…
It’s definitely playing tennis without the net! No cutting forces means the thing just drives back & forth over the platform at warp speed. None of this would make any sense if I were trying to do real subtractive machining … [grin]